A diminutive middle-aged monk was bashed unconscious and left in handcuffs during a violent robbery at a monastery.

Senior Venerable Thich Phuoc An, known as Master An, was seriously injured in the attack at Quan Am Buddhist Monastery south of Auckland.

Police were called to the Bombay Hills monastery on Friday night and the Eagle helicopter was used in an unsuccessful hunt for three men who attacked the monk and robbed the monastery, developed by Master An over the past 15 years.